Full throttle, specific speed tests in internal combustion engine diagnostics

ABSTRACT

Diagnosing an internal combustion engine includes full throttle, specific speed tests such as measuring fuel pressure at two checkpoint speeds and at rated speed, and determining the pressure and speed where the governor reduces fuel pressure, an aneroid checkpoint of fuel pressure as a function of engine speed, and a fuel inlet restriction test, all without a dynomometer. The tests are performed with the throttle wide open, so that pressure can be measured downstream of the throttle at accessible taps, and/or to provide maximum fuel-flow test conditions. The speed comparisons are made during an acceleration with the throttle fully open, the instantaneous speed of which is accurately determined by flywheel tooth sensing. The speeds at which the specification pressure is to be checked is determined by comparing indications related to specification speeds expressed in terms of elapsed time between teeth of the flywheel, for a flywheel having the total number of teeth of the engine under test, rather than requiring full comparisons with actual speed expressed in terms of revolutions per minute.

CROSS REFERENCE TO RELATED APPLICATIONS

Some of the subject matter disclosed herein is disclosed and claimed ina commonly owned copending application filed on even date herewith byWillenbecher et al, Ser. No. 684,036 entitled SPEED-RELATED INDICATIONCOMPARISONS IN INTERNAL COMBUSTION ENGINE DIAGNOSTICS; and the subjectmatter hereof is preferably used in conjunction with the subject matterdisclosed in a commonly owned copending application filed on even dateherewith by Stick et al, Ser. No. 684,037 entitled DETERMINATION OFNUMBER OF TEETH ON AN INTERNAL COMBUSTION ENGINE FLYWHEEL.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to diagnosing internal combustion engineselectronically.

2. Description of the Prior Art

In internal combustion engines, proper operation is related to deliveryof fuel at proper pressures as a function of engine speed, and as afunction of intake manifold pressure. Particularly in the case of dieselengines, the speed of the engine may be controlled by fuel pressure, andoverfueling of the engine, which can result in excessive smoke andpossible engine damage, is prevented by reducing fuel pressure at theinlet to the engine whenever an inadequate air intake pressure exists.

In diesel engines, it has long been known to check fuel pumps againstcertain operating standards, particularly to check the pressure of fueldelivered by the fuel pump at the fuel inlet rail for various speeds ofthe engine (which are herein referred to as the first and secondcheckpoints and the rated point) and the point at which the governorlimits the fuel pressure to avoid excessive engine speed (calledcut-off). However, in the prior art it has been common to remove thefuel pump from the engine and mount it on a specially designed test rigin order to operate the pump at desired speeds in a steady statecondition, and monitor the pressure developed by the pump at thosedesired speeds. This in turn necessitates an excessive amount of laborin removing the fuel pump from the engine, as well as incurring thepotential for inadvertently causing additional problems as a result ofthe mechanical steps involved in the pump removal and reinstallationprocedures.

A seemingly small, but practically troublesome aspect in analyzing fuelsystem is the point at which rail fuel pressure is to be measured. Ifthe pressure measurement is to reflect the pressure of the fuel pumpitself, it must be in full fluid communication therewith; this isparticularly true where the fuel pressure is to be measured under highfueldelivery conditions. On many engines, it is extremely difficult andimpractical to measure fuel pressure upstream of the throttle. In orderto provide adequate pressure measurements, the throttle must thereforebe fully open for on-engine fuel diagnostics. Also, the pump should betested under full flow conditions. Obviously, a vehicle-mounted engineresponding to a fully open throttle will simply advance from low idle togovernor-controlled cut-off speed, at a very rapid rate, which rendersthe measurement of fuel pressures at designated, specification speedsimpossible. To overcome this, it has been known to make open-throttle,steady speed fuel pressure measurements of an engine mounted on avehicle which is standing on a dynomometer. As is known, the dynomometerrotates with the power driving wheels of the vehicle, and can be loadedin a controlled fashion from no load (simulating a slight downgrade) tofull load (simulating a fully loaded vehicle climbing a hill). Thus, thedynomometer load can be adjusted to hold the desired specification speedunder full power, with the throttle wide-open. However, a dynomometer isa very cumbersome and expensive test stand, and is frequently totallyunavailable where vehicle or engine diagnosis is required.

There are other examples of the need to perform open throttle tests atspecified speeds. An aneroid fuel pressure control is normally tested atat least one speed to determine the manner in which fuel pressure varieswith speed when the pressure is also controlled by the aneroid. However,as in the case of fuel pressure tests relating to the fuel pump andother portions of the fuel system, if on-engine testing is to beperformed, it must be done with a full throttle in order to permitmeasuring the fuel pressure, and without a dynomometer to load theengine, full throttle will cause rapid acceleration from idle togovernor cut-off, with no ability to carefully limit operation to adesired speed. A further example is in the testing of the fuel inletpressure (the pressure at the upstream end of the fuel pump, downstreamfrom a fuel filter), the measure of which compared against ambientpressure is an indication of the degree of restriction. But the degreeof restriction as indicated by pressure is also a function of the amountof fuel flowing; therefore full flow pressure is required as a test ofthe fuel inlet restriction. In order to achieve full fuel flow, thethrottle must be open; and, without a dynomometer, the apparatus willsimply accelerate to governor cut-off speed at which point the governorwill reduce the fuel pressure to a very low amount, thereby renderingthe inlet fuel restriction test impossible to perform.

SUMMARY OF THE INVENTION

Objects of the invention include open throttle and full fuel-flowmeasurements of engine parameters without the need of a dynomometer, andimprovements in internal combustion engine fuel pump and other fuelsystem measurements.

According to the present invention, measurements of parameters on aninternal combustion engine are made at specified speeds, during fullthrottle operation of the engine, by allowing acceleration of the engineto occur while repetitively measuring indications of engine speed andmeasuring the speed-related parameters in response to indications thatthe engine has reached the specified speed for the measurement.

According to one aspect of the invention, analysis of a fuel system,including fuel pump pressure measurements as a function of speed, aremade with the fuel pump on-engine, downstream of the throttle, with thethrottle open, by continuously monitoring an indication of speed andsampling fuel pressure in response to sensing a desired related speed ofthe engine.

According to another aspect of the invention, the aneroid pressureregulator of a diesel engine is checked by measuring fuel pressure at aspecification speed with the aneroid operating, the fuel pressure beingmeasured downstream of the throttle while the engine is accelerating ina full fuel, open throttle condition, by continuous measurement of aspeed indication and measuring fuel pressure in response to anindication of the desired speed.

In accordance with another aspect of the invention, measurement of fuelinlet restrictions under full fuel flow conditions is achieved bymeasuring a pressure at the inlet to the fuel pump of an internalcombustion engine while the engine is accelerating in an open throttlecondition, while continuously monitoring indications of speed, andmeasuring the fuel pressure at the inlet to the fuel pump when the speedindications indicate substantially maximum speed below which thegovernor will reduce fuel pressure automatically as a function of speed.

The invention provides capability of monitoring a variety of engineparameters while operating the engine under open throttle conditions,without the need of a dynomometer. The invention further provideson-engine analysis of the fuel system of an internal combustion engineby monitoring pressures at stated speeds, without the need to maintainsteady-state speed conditions. The invention permits onengine diagnosisof the fuel system of an internal combustion engine by monitoringpressures downstream of the throttle, without the need of a dynomometer.The invention provides full fuel flow conditions while monitoringspeed-related parameters of the engine, without the need of adynomometer.

In its broadest sense, the invention permits separating the requirementfor the measurement of certain parameters at given speeds from the needto either operate the engine under steady state speed conditions (whichheretofore has been obtainable only by means of a dynomometer) oroperate the engine components off-engine on a test stand.

Other objects, features and advantages of the present invention willbecome more apparent in the light of the following detailed descriptionof preferred embodiments thereof, as illustrated in the accompanyingdrawing.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a simplified schematic block diagram of a diagnostic systemincluding engine parameter sensing apparatus and exemplary electronicprocessing apparatus, in which the present invention may beincorporated;

FIG. 2 is a simplified block diagram of engine parameter sensingapparatus for use in the embodiment of FIG. 1;

FIG. 3 is a simplified schematic diagram of tooth timer means forobtaining instantaneous, sub-cyclic engine speed in the embodiment ofFIG. 1;

FIG. 4 is a diagrammatic illustration of principles of the invention;and

FIG. 5 is a simplified block diagram of the fuel system of an enginewith probes which may be used in a diagnostic system incorporating theinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIG. 1, a system which may incorporate the presentinvention is illustrated as representing the architecture of a typicaldata processing system or computer together with special purposeapparatus related to an engine diagnostic system of the type in whichthe invention may be incorporated. Specifically, the system incorporatesengine sensors and signal conditioners 10 of a well known type which areadapted to be disposed for response to various parameters or discreteconditions on an engine under test, as described more fully hereinafter.Some of the sensors relate to pressures, temperatures and the like andare therefore analog signals, the magnitude of which is a measure of theparameter being sensed. The outputs of the sensors are fed over lines 13to an analog to digital converter (A/D) 11 when selected by an A/Dmultiplexer 12 in response to a particular sensor address appliedthereto by the program of the data processor. In addition, a toothsensor may sense the passage of teeth on the flywheel of the engine toprovide a tooth signal on line 14, the intertooth time interval of which(when the engine is running) is measured by a tooth timer 15 andprovided on tooth count lines 16. Another discrete signal is a cylinderor cycle identification signal (CID) on a line 17 which is applied to aCID centering circuit 18 to provide a CID signal on a line 19. The rawCID signal on the line 17 is a signal from a proximity sensor disposedto sense movement of an engine member once in each cycle of the engine,such as the rocker arm for the intake valve of one of the cylinders or acam, if desired; this provides information of the cylinder-by-cylinderposition of the engine at any moment in time in the same fashion as thenumber one firing in a spark ignition engine, and also providescycle-to-cycle division of the engine's angular position as it isrunning or cranking.

In accordance with the invention, the parameters of the engine asprovided through the A/D converter 11, and the instantaneous positioninformation with respect to the engine as provided by the CID signal onthe line 17 and the tooth signals on the line 14 may be used indiagnosis of the engine in accordance with the invention herein.

Additional special apparatus which may be used (although as describedhereinafter is not necessarily required) includes a tooth counter anddecode circuit 20, and a pair of counters 20a, 20b referred to ascounter 1 and counter 2, and an internal timer 20c, and special purposeregisters 22, which may be used (as an alternative to memory) to retaincretain factors that are used so often as to render it advisable to havethem directly available to the program rather than having to access themin memory, in order to cut down processing time and complexity ofprogramming. Such registers may contain factors utilized in processingdata (such as multiplicands used in digital filtering of the data andthe like) and information relating to the particular engine under test(such as number of strokes and cylinders) which may be entered byswitches manipulated by an operator, the switches feeding binary decodecircuits such that the decode constantly reflects the position of theswitch on a steady state basis in the manner of a register.

The remainder of FIG. 1 is illustrative of one type of data processingapparatus, which is shwon for illustrative purposes herein since it is atype that may be advantageous for use where general purpose programmingis not required, but rather limited functions are to be performed. Acomputer, as is known in the art, includes memory (or accessiblestorage), and arithmetic unit, program control, and the necessary gates,data flow and event decode or monitoring circuits so as to permitadvancing logically through the steps which are to be performed.Specifically, a memory 24 may be loaded from a variety of inputs shownon the data flow under control of a memory multiplexer 25 which isenabled and addressed by the program so as to select which of thepossible inputs to memory are to be supplied thereto, if any. The memory24 is responsive to a memory address register 26 which may respond to acounter used in program control in a usual fashion. The output of thememory is available to other portions of the data flow, such as printand display apparatus 27 and the arithmetic apparatus includingaritmetic unit input registers, referred to herein as an A register 30and a B register 31 under control of register gates 32 which arecontrolled by the program in a known fashion. Herein, the output of theA register and the B register is available to the register gates 32 andto the main data flow, so that their contents may be moved between theregisters 30, 31 or to the memory 24. This is to facilitate theparticular type of processing which may be employed in an enginediagnostic system, as is described more fully hereinafter. The registers30, 31 feed an arithmetic unit of a known type 35, the function ofwhich, controlled by the program, is to add, substract, multiply ordivide, to provide answers to a result register 36 as well as providingindications of the sign of the result. As indicated in FIG. 1, theresult register may be available at the input to the arithmetic unitthrough the gates 32; alternatively, as is common in many computers theresult register could be automatically one of the inputs to thearithmetic unit, and it can be loaded directly from the memory upon aproper command.

In order to provide data inputs to the memory for initialization and topermit a degree of control over the system during processing, a keyboard38 of a usual variety may be provided. In addition to data inputs, thekeyboard may have control function keys that permit choice to theoperator of loading memory from the result register or of loading memoryin response to the keyboard, depending upon conditions which may bedisplayed in the print and display apparatus 27.

For the rather limited number of tests being performed in apparatusincorporating the present invention, the program may be controlled in avariety of ways. One way is a program ROM 40 which provides input gateaddresses to control the inputs to the memory, the arithmetic inputregisters, and the A/D converter, etc.; the memory address; thefunctions to be performed by the arithmetic unit, and other commandssuch as commands to the memory to cause it to read or write, and tostart the A/D converter 11, and the like. Sequencing is controlled byunconditioned branch instructions (which provide a branch address) andby skip instructions (dependent on conditions) provided to a branch/skipcontrol 42 at the input to the program counter 44, which is alsoresponsive to system clocks 46. Thus, as is known, for each programclock signal received from the system clocks, the program counter may beadvanced, skipped once or twice, or reset to the branch address, independence upon the presence of branch or skip instructions.

It should be understood that the particular processing apparatus used,and the degree of use of special purpose apparatus, is dependent uponthe particular implementation of the present invention which is to bemade, and forms no part of the present invention. If the invention isutilized in a complex, sophisticated diagnostic system in which avariety of diagnostic functions are required, then the type of apparatusselected for processing may be more sophisticated and capable of generalpurpose utilization in order to accommodate the special requirements ofall of the diagnostic procedures to be performed. However, the cost ofprogramming complexity of such a processing system may be unwarranted ina diagnostic system which performs either relatively few or relativelysimple tests. As is more apparent in the light of detailed operationaldescriptions hereinafter, well known processing systems (such as NOVA adPDP/11) employing only programs provided through techniques well knownin the art, may be utilized in conjunction with the engine sensors andconditioners 10, suitable input and output apparatus (such as thekeyboard 38 and the print and display apparatus 27) and, depending onthe processing power of the data processing system selected, somespecial purpose hardware which may be found advisable, such as the toothtimer 15, the tooth counter 20 and some special registers 22. However,the well known processing systems referred to hereinbefore can provideadequate memory capacity to perform the tooth timing and countingfunctions, and to provide for the storage of all required parameters andengine information in the memory, as is readily apparent to thoseskilled in the art.

Referring now to FIG. 2, a plurality of engine sensors in a diagnosticsystem incorporating the present invention may include, among others notshown in FIG. 2, a starter voltage probe or clamp 46, a starter currentprobe 47, an atmospheric pressure transducer 48, which could be disposedin general proximity to the engine under test, a pressure transducer 49to measure the intake manifold air pressure, a filter pressuretransducer 50 to measure the pressure of the fuel downstream of the fuelinlet filter, a fuel pressure transducer 51 to measure the pressure atthe fuel injector inlet rail of the engine, a coolant pressuretransducer 52 which may preferably measure the pressure of coolant atthe inlet to the coolant thermostat, a coolant temperature transducer 53to measure coolant temperature, preferably at the inlet to thethermostat. In a diagnostic system incorporating the present inventionthere may also be a proximity sensor 54, which may comprise an RGT Model3010-AN Magnetic Proximity Sensor, provided by Electro Corporation,Sarasota, Florida, for sensing the passage of flywheel teeth past aparticular point adjacent to the flywheel housing, and a proximitysensor 55 such as Model 4947 Proximity Switch distributed by ElectroCorporation, for sensing the presence of an engine member which moves ina unique fashion once in each cycle of the engine, which is onerevolution in a two stroke engine or two revolutions in a four strokeengine. The proximity sensor 55 may preferably be mounted through thevalve cover adjacent to a rocker arm related to the intake valve of oneof the cylinders of the engine, thereby to provide information as to theparticular point of an engine cycle once in each cycle, as well as todelineate successive engine cycles as the engine is rotating.

Each of the sensors of FIG. 2 is applied to a suitable one of aplurality of signal conditioners 56, 57 to filter out unwanted noise,and to provide, through an amplifier, suitable level adjusting as isappropriate for the circuitry being fed thereby. For instance, thesignal conditioners 56 scale the signals to the proper level so thateach of them can be fed through a common A/D converter 12 (FIG. 1). Thesignal conditioners 56, 57 can be suitable ones of a wide variety knownin the art, and form no part of the present invention.

Referring now to FIG. 3, the tooth timer 15 includes a counter 60 whichrepetitively counts clock pulses on a line 61 that may be supplied bysystem clocks 46 in FIG. 1. The counter is parallel-fed to a buffer 62,the output of which comprises the tooth counts. The counter is runningsubstantially all of the time since a very high frequency clock signalcan be utilized on the line 61 (anywhere form tens of KHz to tens ofMHz) whereas at speeds from 300 rpm to 2,000 rpm the frequency of thetooth signals on the line 14 may be on the order of 10 Hz to 100 Hz,depending upon the number of teeth. Thus the few clock signals lostduring the tooth to tooth resetting of the counter are miniscule.

Each time that a tooth signal appears on the line 14, the next clocksignal will set a D-type flip flop 63, the Q output of which is appliedto a D-type flip flop 64. The second clock signal following the toothsignal therefore sets the D-type flip flop 64, and since its Q output isapplied to a D-type flip flop 65 the third clock signal will cause it tobecome set. The very first clock signal, after the appearance of thetooth signal, is decoded by an AND circuit 66 since it responds to Q offlip flop 63 and not Q of flip flop 64 and 65; this provides a loadbuffer signal on a line 67 to cause the buffer 62 to be loaded inparallel from the counter 60. The second clock signal following theappearance of the tooth signal will cause an AND circuit 68 to respondto the Q of flip flops 63 and 64 and the not Q of flip flop 65 so as togenerate a clear counter signal on a line 69 which is applied to theclear input of the counter 60 causing it to be cleared to zero. Thethird clock signal, by setting the flip flop 65, simply eliminates theclear counter signal on the line 69 so that the next leading edge of theclock signal and all subsequent clock signals will be counted in thecounter 60. Whenever the tooth signal disappears, (which is totallyimmaterial) the next three clock signals in a row will cause resettingof the flip flops 63-65, in turn, since each of their D inputs will godown. The counter and the buffer are independent of the resetting of theflip flops 63-65 since both AND circuits 66, 68 operate only during aprogression with flip flop 63 on and flip flop 65 off, which does notoccur during the resetting of the flip flops.

Thus the tooth timer 15 provides tooth counts on the line 16 which arestable, throughout substantially each intertooth interval. Theprocessing apparatus of FIG. 1 may therefore sample the tooth counts atrandom. The tooth timer 15 thereby provides very accurate, subcyclicspeed measurement, on a tooth to tooth basis, which provides speedindications many times within each individual cylinder stroke portion ofeach engine cycle.

In the detailed description of exemplary processing hereinafter, theterm "ringgear" is sometimes used in place of "flywheel"; they mean thesame thing; the abbreviation "RGT" means "ringgear teeth", a storedfactor indicating the number of teeth on the flywheel of the engineunder test. This may be determined and entered from enginespecifications, or as set forth in a commonly owned copendingapplication of Stick et al, Ser. No. 684,037, entitled "Determination ofNumber of Teeth on an Internal Combustion Engine Flywheel". Otherabbreviations include: "RSLT"=result register; "MEM"= memory; "Ctr" =counter; "Factor" means a memory location or a register where the factoris available; "CMPLT" means A/D conversion is completed; "spd" meansspeed; and other abbreviations are apparent in the drawing.Parentheticals after "MEM", such as "(Freq)", indicate addresses, chosenat will by the programmer, or partially determined by counter two, if soindicated.

The exemplary system herein is designed for fourstroke, six-cylinderengines. If desired, the programming may be altered to compare counts(particularly counter two) with loaded indications of engine variables,such as cylinders, in a well known fashion.

Referring now to FIG. 4, several of the full-throttle, specific speedtests of the present invention, relating to fuel system health, areillustrated. In a first test, the aneroid is defeated so that it willnot limit fuel supplied to the engine during a snap acceleration, andfuel pressure is measured at three speeds (checkpoint one, checkpointtwo, and rated speed) as determined by manufacturer's specifications forthe given fuel system. In addition, the speed at which the governor cutoff comes into play to limit engine speed is determined by measuring themaximum pressure before the pressure starts to trail off.

In a second test, the aneroid is reconnected, and the fuel pressure ismeasured at about halfway between low idle and high idle speeds, asillustrated in FIG. 4. A third test, not illustrated in FIG. 4, measuresthe restrictive effect of the fuel filter by measuring the pressuredownstream of the fuel filter but upstream of the fuel pump, when in afull fuel flow condition, which is taken herein to be rated speed.

Referring to FIG. 5, a fuel tank 100 feeds a fuel filter 102 which feedsa fuel pump 104, which is typically a gear-type pump. Between the filter102 and the pump 104, the filter pressure transducer 50 is tapped in.From the pump 104, the fuel passes through a pressure regulator 106,which is typically formed as an integral part of the fuel pump. From thefuel pressure regulator, a bypass is provided through an aneroid 107back to the tank 100 to bypass fuel in a manner which is inverse to theintake manifold air pressure, as is known in the art. In other words,when there is little air pressure provided by the turbocharger at theintake manifold, then less fuel is allowed to pass to the throttle 108.Downstream of the throttle 108, at the fuel injector inlet rail 110 thefuel pressure transducer 51 is tapped in. The arrangement of FIG. 5 isnot critical to the invention, however FIG. 5 is illustrative of certainof the problems relating to full fuel, specific speed tests, and moreparticularly to problems which may be encountered in diagnosing thehealth of a fuel system, all as is described hereinbefore.

The speed measurements herein are made by the tooth timer, which sensesthe passage of teeth and records a count of the number of clock signalsfed to a counter on a tooth-to-tooth basis. The number of ringgear teethcan be determined from manufacturer's specifications and provided ineither a register or a predetermined location in memory prior to thetest. Or, if desired, the teachings of the aforementioned Stick et alapplication may be utilized to determine the number of ringgear teeth(RGT) on the flywheel and have that available in memory; none of thisforms any part of the present invention. The fraction of a revolutiontraversed as each tooth passes the sensor is simply the ratio of onedivided by the total number of teeth. The time for that fraction of arevolution to occur is simply the counts of the interval timer dividedby the frequency of clock signals fed to the interval timer. Sincefrequency of the clock feeding the counter is expressed in Hz, and speedis normally expressed in revolutions per minute, a factor of 60 must beemployed in a well known fashion. To actually determine the speed fromthe counts provided by the tooth counter the relationship is the ratioof one tooth to the total number of teeth, which is divided by the ratioof the counts to the frequency (the frequency in turn having to be firstdivided by 60 to yield a result in rpm's). Rewritten this results in thefrequency of the clock times 60, all of which is divided by the totalnumber of flywheel teeth times the counts in the timer. This may bepredetermined as a speed factor, so that any time a speed reading isrequired (such as at governor cut off herein), it can be taken simply bydividing the speed factor by the number of counts in the timer,according to the following instructions:

1. Load MEM (Freq) to A REG

2. Load MEM (RGT) to B REG

3. Divide

4. Load RSLT to A REG

5. Load 60 Factor to B REG

6. Multiply

7. Load RSLT to MEM (Spd Factor)

On the other hand, when comparing the actual speed of the engine asdetermined by the tooth timer with predetermined speeds (such ascheckpoints one and two, and rated speed herein) one can reverse theposition of speed and counts in the relationships described hereinbeforeand determine in advance the number of counts which the tooth timer willhave when the engine has a predetermined speed. This is done generallyby multiplying the frequency of the clock times 60, all of which isdivided by the product of the total number of teeth on the flywheel andthe desired starting speed in rpm. This can be accomplished in theexemplary diagnostic system of FIG. 1, assuming the specification speeds(checkpoint one, checkpoint two, and rated speed) are available inmemory, with the following instructions:

8. Load MEM (Freq) to A REG

9. Load MEM (RGT) to B REG

10. Divide

11. Load RSLT to A REG

12. Load MEM (Check 1 Spd) to B REG

13. Divide

14. Load RSLT to A REG

15. Load 60 Factor to B REG

16. Multiply

17. Load RSLT to MEM (Check 1 Factor)

In a similar fashion, factors may be precomputed for checkpoint two andfor rated speed as follows:

18. Load MEM (Freq) to A REG

19. Load MEM (RGT) to B REG

20. Divide

21. Load RSLT to A REG

22. Load MEM (Check 2 Spd) to B REG

23. Divide

24. Load RSLT to A REG

25. Load 60 Factor to B REG

26. Multiply

27. Load RSLT to MEM (Check 2 Factor)

28. Load MEM (Freq) to A REG

29. Load MEM (RGT) to B REG

30. Divide

31. Load RSLT to A REG

32. Load MEM (Rated Spd) to B REG

33. Divide

34. Load RSLT to A REG

35. Load 60 Factor to B REG

36. Multiply

37. Load RSLT to MEM (Rated Factor)

Then the system can simply monitor the tooth timer counts, continuouslysubtracting the tooth timer counts from the predetermined counts. Sincecounts become smaller and smaller as the speed increases, when the speedof the engine exceeds the predetermined speed, then the predeterminedcounts will exceed the tooth timer counts and this can be determined bydoing a reverse subtract and looking for a negative result.

In the following, it is assumed that the fuel pressure test has a baseaddress in memory, and the specific points being accommodated can beindexed with counter 2. Thus the checkpoint speeds, referred toinstructions 8-37 hereinbefore, may have been stored at the base addresswith counter number 2 as the specific address for the checkpoint speed,such as (check 1 spd), as in instruction 12. Then, the factors couldhave been stored back into the same point simply by keeping track of thethree factors by means of counter 2. This mode is illustrated in theinstructions which follow, bearing in mind that the counter 2 address isnow assumed to be the address where the check factors and rated factorare stored, and where the result will end up. However, separateaddresses could be utilized, through programming techniques well knownin the art.

This test must be performed with the engine accelerating, and it isobviously known when the engine is accelerating since the operator mustpress the throttle to cause the snap acceleration. Thus the operatorwill start the test, the preliminaries referred to hereinbefore will beperformed as the operator pushes the throttle down, and as theaccelerations actually begin, speed is monitored and pressure readingsare taken; two speeds in excess of the rated speed being measured beforethe pressure reading is taken to be assured that a noise spike hasn'tcaused an erroneous sensing of the desired speed (the slight delay isinconsequential, due to commensurate delays in the reading of the fuelpressure as a consequence of long lines, analog signal filters and thelike).

Since one of the full throttle, specific speed tests herein is measuringfilter restriction at maximum fuel flow, the filter pressure transducercan be sampled at rated speed, and the results stored. This is donefollowing rated speed fuel pressure, at instructions 56-60.

Exemplary instructions are:

38. Reset Counter 2

39. Reset Counter 1

40. Advance Counter 2

41. Load MEM (Ctr 2) to B REG

42. Load Tooth timer to A REG

43. Subtract

44. Skip two if-

45. Reset Counter 1

46. Branch to 42

47. Advance Counter 1

48. Skip 1 if Counter 1 = 2

49. Branch to 42

50. A/D MPX to Fuel Pres

51. Start A/D

52. Skip one if CMPLT

53. Branch to 52

54. Load A/D to MEM (Ctr 2)

55. Skip one if Counter 2 = 4

55a. Branch to 39

56. A/D MPX to Filter Pres

57. Start A/D

58. Skip one if CMPLT

59. Branch to 59

60. Load A/D to MEM (Filter Pres)

Once the pressure versus specific speed measurements have been made, thepresent invention can then provide a measure of the speed at which thegovernor cut-out reduces fuel pressure, thereby regulating the maximumspeed of the engine. To do this, pressure is measured as fast as the A/Dcan measure it, although any short time interval could be included todelay if desired. For each pressure measurement made, the subsequentpressure measurement must be at least 2 psi (or such other factor as isdetermined upon in any implementation of the present invention) belowthe preceding measurement. Thus each measurement brought in is comparedagainst the previous one less 2 psi, and then it has 2 psi subtractedfrom it for comparison with the next measurement, and so forth. When twomeasurements made in turn are 2 psi below the preceding measurement, thespeed relating to the first such pressure is taken as the regulatorspeed, and this is saved for subsequent use. However, the pressuremeasurements made in this portion of the test are irrelevant.

Speed is measured in the manner described hereinbefore, utilizing thespeed factor which has been stored in memory by instruction 7. To keeptrack of the speeds with each pressure measurement, since the desiredspeed won't be known until two additional pressure measurements aretaken, and therefore at least three speeds must be available as the testproceeds towards the desired speed, a base address can be utilized inthe fashion described hereinbefore with counter 2 used as an indexaddress while counter 1 keeps track of the number of tests. In theexemplary process set out hereinafter, the first measurement made willbe subtracted from -2 psi, since it will be made against no previousreading. However this will automatically fail the test so there is noproblem. Thereafter legitimate testing is done in response to each loopthrough the subroutine, as follows:

61. Reset Counter 1

62. Reset Counter 2

63. Advance Counter 2

64. Start A/D

65. Load Tooth timer to MEM (Ctr 2)

66. Load 2 PSI Factor to B REG

67. Subtract

68. Load RSLT to B REG

69. Skip one if CMPLT

70. Branch to 67

71. Load A/D to A REG

72. Subtract

73. Skip two if -

74. Reset Counter 1

75. Branch to 63

76. Advance Counter 1

77. Skip one if Counter 1 = 2

78. Branch to 63

79. Load MEM (Ctr 2) to Print and Display

Another full throttle, specific speed test which the present inventionperforms is sensing the fuel rail pressure at an aneroid checkpoint, asdescribed previously with respect to FIG. 4. This utilizes the samepressure sensor, and is exactly the same as the checkpoint testperformed hereinbefore. However, the aneroid defeat (shop air connectedto the aneroid) should be removed and the aneroid connected to theintake manifold for proper operation. Since the loading of the engine isrelatively light, during the snap acceleration used in the aneroid test,the amount of energy in the exhaust gas of the engine isn't sufficientto drive the turbocharger very hard, so that the intake manifoldpressure remains relatively low throughout the snap acceleration.However, from one engine to the next, the aneroid checkpoint provides avery good test of the health of the aneroid by measuring fuel pressureat a speed which is roughly halfway between low idle and high idle, asillustrated in FIG. 4. Since only a single test need be made, the speedfactor (as described with respect to instructions 8-37 hereinbefore) cansimply be saved in the B register, and then the tooth timer can becompared therewith as follows:

80. Load MEM (Freq) to A REG

81. Load MEM (RGT) to B REG

82. Divide

83. Load RSLT to A REG

84. Load MEM (Aner Spd) to B REG

85. Divide

86. Load RSLT to A REG

87. Load 60 Factor to B REG

88. Multiply

89. Load RSLT to B REG

90. Reset Counter 1

91. Load Tooth timer to A REG

92. Subtract

93. Skip one if -

94. Branch to 91

when the speed is actually sensed, all that is required is simply tostore the pressure at the fuel rail at that point in time (in the samefashion as described hereinbefore), exemplary instructions for whichare:

95. Advance Counter 1

96. Skip 1 if Counter 1 = 2

97. Branch to MEM 91

98. A/D MPX to Fuel Pres

99. Start A/D

100. Skip one if CMPLT

101. Branch to 100

102. Load A/d to (Aner Spd)

Although the invention has been shown and described with respect toexemplary embodiments thereof, it should be understood by those skilledin the art that the foregoing and various other changes, additions andomissions may be made therein and thereto without departing from thespirit and the scope of the invention.

Having thus described typical embodiments of our invention, that whichwe claim as new and desire to secure by Letters Patent is:
 1. Apparatusfor testing an internal combustion engine while operating under openthrottle conditons without the need of a dynomometer,comprising:transducer means adapted to be disposed for response to anengine-related parameter, a measurement of which is desired with theengine operating under open throttle conditions; speed sensing meansadapted to be disposed to sense rotation of the engine under testthrough an angular increment which is substantially less than arevolution of the engine as related to time in a fashion to provide anindication of speed on a sub-revolution basis; and processing meansresponsive to said speed means for successively monitoring the speedindication provided by said speed sensor means as said engine isaccelerating and, in response to said indications indicating that theengine has reached a speed in excess of a predetermined speed, samplingthe output of said transducer means.
 2. Apparatus according to claim 1wherein said processing means includes means for registering anindication of a predetermined speed and means for continuously comparingsaid predetermined speed indication with said engine speed indicationssuccessively presented by said speed means.
 3. Apparatus according toclaim 2 wherein said predetermined speed indication is an indication ofsubstantially the maximum speed of the engine below governor cut-offspeed.
 4. Apparatus according to claim 3 wherein said predeterminedspeed indication is an indication of rated engine speed.
 5. Apparatusaccording to claim 2 wherein said speed indication is one of a pluralityof checkpoint speeds included in the speed-pressure specification of thefuel pump of the engine, and wherein said transducer means comprises afuel pressure transducer disposed downstream of a throttle in the fuelpressure system of said internal combustion engine.
 6. Apparatusaccording to claim 2 wherein said speed indication is a checkpoint speedincluded in the speed-pressure specification of the aneroid of theengine, and wherein said transducer means comprises a fuel pressuretransducer disposed downstream of a throttle in the fuel pressure systemof said internal combustion engine.
 7. Apparatus according to claim 1wherein said transducer comprises a fuel pressure transducer adapted tobe disposed between the fuel inlet filter and the fuel pump inlet of aninternal combustion engine and wherein said processing means includesmeans for registering the rated speed of said engine and providing saidpredetermined indication in response thereto, the apparatus therebyproviding a measure of the pressure rise from ambient across the inletfilter of a fuel system while said fuel system is deliveringsubstantially maximum fuel.
 8. In the method of making speed-regulatedmeasurements of parameters of an internal combustion engine while theengine is operating under open throttle conditions, the stepsof:operating the engine with the throttle wide open and allowing theengine to accelerate from idle to its maximum unloaded speed;continuously monitoring the speed of the engine by sensing a speedindication derived from a moving member on said engine; continuouslycomparing the speed indications as provided with test speed indicationsindicative of speeds at which the parameter of the engine is to bemeasured; and measuring the parameter of said engine in response to saidcomparisons indicating that the speed of the engine has reached thecorresponding test speed.
 9. Apparatus for testing an internalcombustion engine while operating under open throttle conditions withoutthe need of a dynomometer, comprising:a fuel pressure transducer meansdisposed downstream of the throttle in the fuel pressure system of saidinternal combustion engine; speed sensing means adapted to be disposedto sense rotation of the engine under test through an angular incrementwhich is substantially less than a revolution of the engine as relatedto time in a fashion to provide an indication of speed on asub-revolution basis; and processing means responsive to said speedmeans and to said transducer for successively monitoring the speedindications provided by said speed sensor means and the output of saidtransducer as said engine is accelerating and for determining inresponse thereto the speed at which the pressure in the fuel system ismaximum.
 10. In the method of making speed-related measurements ofparameters of an internal combustion engine fuel system, the stepsof:operating the engine with the throttle wide open and allowing theengine to accelerate from idle to its maximum unloaded speed;determining the maximum fuel pressure of the engine as it accelerates;and sensing the speed of the engine at which maximum fuel pressure issensed.
 11. In the method of measuring fuel pump inlet restriction of aninternal combustion engine under full fuel flow conditions, the stepsof:operating the engine with the throttle wide open and allowing theengine to accelerate from idle to its maximum unloaded speed;continuously monitoring the speed of the engine by sensing a speedindication derived from a moving member on said engine; continuouslycomparing the speed indications as provided with a speed indicationindicative of substantially the maximum rated speed; and measuring thepressure at the inlet to the fuel pump of said engine in response tosaid comparisons indicating that the speed of the engine has reachedsubstantially the maximum rated speed.